Oscillation generation



May 19, 1931. A. MEISSNER OSCILLATION GENERATION.

Filed Oct. 20. 1928 gig m VIE??? LI F INVENTOR AL XANDE MEISSNER BYAQNEY waves.

patented May 19, 193i UNETED STATES ALEXANDER MEISSNER, OF BERLIN,GERMANY, 'ASSIGNORTO TELEFUNKEN GES ELL- 7 PATENT OFFICE SCI-IAFT FURDRAHTLOSE TELEGRAPHIE M. B. H. HALLESCHES, OF BERLIN, GER- MANY, ACORPORATION OF GERMANY oscILLArron GENERATION Application. filed October20, 1928, Serial No.

This invention relates to the generation of oscillations, and moreparticularly to the generation, alternately, of oscillations ofdifferent frequencies, for the reduction of fading.

The object of the present invention is to provide a transmitterarrangement for wireless communication especially on extra-short It is awell-known fact that when working with short waves disturbances intraflic are often produced because the income ing signal strengthbecomes periodically or transiently very small or even drops to zero.Such variationsv in intensity, known as fading, are substantially due tointerference phenomena. In order to eliminate them it is suggested tosend the same signals simultaneously on carriers of two or morefrequencies, inasmuch as fading depends upon the frequency that is used,so that, if two or more different wave-lengths are employed,simultanenous extinction of both or all of these frequencies is not tobe anticipated.

Now, in order that it may be feasible to receive signals sent out on,say, two waves, with one receiver, and to economizein the use ofavailable signalling frequencies, it is a. preferable plan to utilizetwo frequencies which are but slightly different from each other. At thetransmission end the generation of such closely adjacent frequenciesgives rise to the difficulty that the two transmitters are subject tomarked mutual interference, so that the oscillations of one of thesetransmitters, under certain circumstances, may be .entrained by or fallinside the range of forced oscillations of the respective othertransmitter tube, with the result that, instead of the intended twofrequencies, only one frequency is sent out.

In order to overcome these practical difliculties, according to thedisclosure of the present invention, the two thermionic tubes providedto generate or amplify the different frequencies are supplied from analternating current source in push pull or phase opposition, so that theplates of the two transmitters are alternately fed with the positivehalfcycles required for the production of oscillations. In this way, allchances of one of the tubes happening to fall inside the range of313,703, and in Germany November 24, 1927.

not to speak of the fact that the use of sucha 1 working potentialoffers this further merit that the working potential changes inside ahalf-wave in its intensity whereby a modulation of the radio frequencysent is caused. Radio frequency waves modulated by alternating current,as has been found by tests, are subject to less fading, seeing that themodula-.. tion itself produces a decomposition or division of thefrequency.

The specification is accompanied by ings, in which d Figure 1 is awiringdiagram for one form of my invention; and p I v Figure 2 is amodification in which the frequency change is obtained in amplifierstages.

An arrangement according to this invention which may be regarded as anembodiment of the idea chosen by way of example is illustrated in theaccompanying drawings. Two thermionic tubes E1 and E2 are connectedtransmitter fashion and are made to work upon two antennae A1 and A2.One of these thermionic tubes, E1, contains in its plate circuit anoscillation circuit S1, and in its grid circuit an oscillation circuit81, which are tuned to one of the waves, while the other thermionic tubehas two similar oscillatory circuits S2 and 82 which are tuned to theother wave to be generated. The working potentials for these two tubesare furnished y way of transformer T from an alternating current source,as shown. The ends of the secondary winding T of said transformer areunited with the two plates, while the middle point of the transformerisassociated with the two filaments. To shut off the alternating currentoperating current from the oscillation circuits carrying the radiofrequency currents, blocking condensers K are provided.

It will be understood that, within the spirit of this invention, variousother circuit arrangements arefeasible. For instance, arrangements couldbe made also so that the two thermionic tubes whose plates are suppliedwith alternating current potentials in phase opposition, are separatelycontrolled. In this case, the tubes themselves do not act as generators,but as amplifiers,

Such an arrangement is indicated in Figure 2, which is quite similar tothe arrangement shown in Figure 1 except that in this case the tubes E1and E2 are amplifier tubes, rather than oscillator tubes. The energiesof different frequencies are first generated in master oscillators M1and M2, and these are separately fed to the tuned input circuits of theamplifiers. It will be noticed that in this case the output circuits S1and S2 are both amplifiers which have been shown coupled to a singleantenna A instead of two separate antennas, but, of course, this featureis applicable to either arrangement,

I claim:

A transmission system for reducing the effect of fading comprising afirst master oscillator for generating a first frequency, a first spacedischarge device amplifier circuit having input and ouput circuits tunedto said first frequency adapted to amplify the oscillations generatedfrom said first oscillator, a second master oscillator for generating asecond frequency, a second space discharge device amplifier circuithaving input and output circuits tuned to said second frequency adaptedto amplify the oscillations generated from said first oscillator, analternating current source coupled in push-pull to the output circuitsof said space discharge device amplifiers so that said amplifiers aremade operative alternately, and means to radiate the resulting energyfrom both said amplifiers.

ALEXANDER MEISSNER.

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